1. Field of the Invention
The present invention relates generally to the field of paper trays for printers, copies, and the like. More specifically, the present invention discloses a paper tray with tray guides that automatically adjust to accommodate a range of media sizes.
2. Statement of the Problem
Many sheet-fed devices, such as printers, scanners, copiers, fax machines, and the like, must accommodate a variety of different media sizes. The conventional approach has been to equip these devices with a paper tray having movable tray guides that can be manually adjusted by the user for different media sizes.
The prior art in this field also includes several patents that disclose paper trays that automatically adjust the positions of the tray guides to accommodate different media sizes. For example, U.S. Pat. No. 5,360,207 (Rauen et al.) and U.S. Pat. No. 5,110,106 (Matsumura et al.) disclose automatically-adjusting paper trays that use pressure transducers to sense when the guides are brought into contact with the edges of the media stack. However, this approach has a basic limitation in that a short stack of paper containing only a few sheets may not be sufficient to trigger the pressure sensors on the tray guides. Instead, the media will tend to bow or distort, thereby creating the risk of a paper jam or a misfeed. Therefore, a need continues to exist for an automatically-adjusting paper tray capable of handling a wide variety of media sizes and stacks of any thickness.
3. Solution to the Problem
None of the prior art references discussed above show an automatically-adjusting paper tray that employs arrays of photodetectors on the floor of the paper tray to sense the edges of the media.
This invention provides a paper tray that automatically adjusts to accommodate a variety of media sizes. An array of photodetectors on the support surface of the tray are masked from light by placing media in the tray. A controller determines the size of the media by monitoring which photodetectors have been masked. The controller can then direct tray guides to move to predetermined positions corresponding to the dimensions of the media.
These and other advantages, features, and objects of the present invention will be more readily understood in view of the following detailed description and the drawings.